Bleaching enzymes such as peroxidases together with hydrogen peroxide or oxidases together with oxygen have also been suggested for bleaching of dyed textiles (see WO 92/18683), either alone or together with a phenol such as p-hydroxycinnamic acid, 2,4-dichlorophenol, p-hydroxybenzene sulphonate, vanillin or p-hydroxybenzoic acid.
Dyeing of textiles is often considered to be the most important and expensive single step in the manufacturing of textile fabrics and garments. The major classes of dyes are azo (mono-, di-, tri-, etc.), carbonyl (anthraquinone and indigo derivatives), cyanine, di- and triphenylmethane and phthalocyanine. All these dyes contain chromophoric groups which give rise to color. There are three types of dyes involving an oxidation/reduction mechanism, i.e., vat, sulfur and azoic dyes. The purpose of the oxidation/reduction step in these dyeings are to change the dyestuff between an insoluble and a soluble form.
Oxidoreductases, e.g., oxidases and peroxidases, are well known in the art. WO 91/05839 discloses that oxidases and peroxidases are useful for inhibiting the transfer of textile dyes. One class of oxidoreductases is laccases (benzenediol:oxygen oxidoreductases) which are multi-copper containing enzymes that catalyze the oxidation of phenols and related compounds. Laccase-mediated oxidation results in the production of aromatic radical intermediates from suitable substrates; the ultimate coupling of the intermediates so produced provides a combination of dimeric, oligomeric, and polymeric reaction products. Such reactions are important in nature in biosynthetic pathways which lead to the formation of melanin, alkaloids, toxins, lignins, and humic acids. Another class of oxidoreductases are peroxidases which oxidize compounds in the presence of hydrogen peroxide. Saunders et al., Peroxidase, London, 1964, p. 10 ff. disclose that peroxidases act on various amino and phenolic compounds resulting in the production of a color.
Laccases have been found to be useful for hair dyeing. See, e.g., PCT applications Ser. No. PCT/US95/06815 and PCT/US95/06816. European Patent No. 0504005 discloses that laccases can be used for dyeing wool at a pH in the range of between 6.5 and 8.0.
Japanese Patent Application publication no. 6-316874 discloses a method for dyeing cotton comprising treating the cotton with an oxygen-containing medium, wherein an oxidation reduction enzyme selected from the group consisting of ascorbate oxidase, bilirubin oxidase, catalase, laccase, peroxidase, and polyphenol oxidase is used to generate the oxygen.
Discharge printing is a method of obtaining printed images on a fabric surface by selectively removing dye from a dyed fabric. For example, indigo dye can be discharged by transforming the indigo into yellow, water-soluble stain by oxidation or by reforming leuco-indigo which can be readily removed from fiber by alkali treatment. Generally, three methods of oxidation discharge printing are used commercially: chromate, chlorate, and prussiate discharge.
Reduction discharge of indigo dyeings is based on the reducing action of hydrosulfite on vat dyes and is carried out in the same manner by printing discharge paste on the fabric, aging the printed fabric, and exposing the printed fabric to a caustic soda or sodium silicate bath in order to dissolve the reduced indigo from the printed parts of the fabric. Of commercial importance is the use of hydrosulfite discharge of indigo.